Postoperative Endometrial Carcinoma Treated with External Beam Irradiation Plus Vaginal-Cuff Brachytherapy. is There a Dose Relationship with G2 Vaginal Complications?

Aim: To analyse the possible relationship between the EQD2((alpha/beta=3Gy)) at 2 cm(3) of the vagina and late toxicity in vaginal-cuff-brachytherapy (VBT) after external-beam-irradiation (EBRT) for postoperative endometrial carcinoma (EC). Materials and methods: From 2014 to 2016, 62 postoperative EC patients were treated with EBRT + VBT. The median EBRT dose was 45 Gy (44 Gy-50.4 Gy). VBT involved a single 7 Gy dose. Toxicity was prospectively evaluated using the RTOG score for the rectum and bladder and the objective LENT-SOMA criteria for the vagina. EQD2((alpha/beta=3Gy)) at 2 cm(3) of the most exposed part of the vagina was calculated by the sum of the EBRT + VBT dose. Statistics: Boxplot, Student's t and Chi-square tests and ROC curves. Results: Mean follow-up: 39.2 months (15-68). Late toxicity: bladder:0 patient; rectum:2 patients-G1; Vagina: 26 patients-17G1, 9G2; median EQD2((alpha/beta=3Gy)) at 2 cm(3) in G0-G1 patients was 70.4 Gy(SD2.36), being 72.5 Gy(SD2.94) for G2p. The boxplot suggested a cut-point identifying the absence of G2: 100 % of G2p received >68 Gy, ROC curves showed an area under the curve of 0.72 (sensitivity of 1 and specificity of 0.15). Conclusions: Doses >68 Gy EQD2((alpha/beta=3Gy)) at 2 cm(3) to the most exposed area of the vagina were associated with late G2 vaginal toxicity in postoperative EC patients treated with EBRT + VBT suggesting a very good dose limit to eliminate the risk of G2 late toxicity. The specificity obtained indicates the need for prospective analyses. (C) 2020 Greater Poland Cancer Centre. Published by Elsevier B.V. All rights reserved.